1. Field of the Invention
The present invention relates to a novel liquid crystalline polyester resin composition which can be formed in a molded article by injection or extrusion molding and has good heat resistance, moldability and mechanical properties, in particular, impact resistance.
2. Description of the Related Art
Since molecules of a liquid crystalline polyester are stiffer than those of a crystalline polyester such as polyethylene terephthalate or polybutylene terephthalate, they do not tangle each other in a molten state and form a polydomain having a liquid crystalline state. Then, molecule chains of the liquid crystalline polyester are strongly orientated in a flow direction under low shear and it is called as a "thermotropic liquid crystalline polymer". Because of such specific behavior, the liquid crystalline polyester has excellent melt flow characteristics and can easily provide a molded article having a thin wall of, for example, 0.2 to 0.5 mm. In addition, the molded article is characterized in high strength and high stiffness. However, the liquid crystalline polyester has some drawbacks such as extremely large anisotropy and considerably low weld strength. Further, since the liquid crystalline polyester has a high molding temperature, its application is limited. It is also a problem that a liquid crystalline polyester is expensive in general.
Accordingly, it is highly desired commercially to provide a liquid crystalline polyester resin composition which has improved weld strength and is cheap while maintaining good heat resistance and mechanical properties of the liquid crystalline polyester.
EP-A-030 417 discloses a resin composition comprising a melt-processable polymer and a polymer which forms an anisotropic melt and describes that the addition of the polymer which forms an anisotropic melt to the melt-processable polymer improves the processability of the latter. For example, the addition of a liquid crystalline polyester to a mixture of polyphenylene ether and polystyrene is disclosed.
Japanese Patent Kokai Publication No. 97555/1990 discloses a resin composition comprising a liquid crystalline polyester and various polyarylene oxides which improve heat resistance in soldering.
While a composition comprising the liquid crystalline polyester having a high molding temperature and an amorphous crystalline polymer having a lower molding temperature such as polyphenylene ether may improve the melt processability, it will provide a molded article with deteriorated appearance due to thermal decomposition of the amorphous polymer caused by high temperature in the molding step. In addition, such composition has insufficient heat resistance, mechanical properties or impact strength.